CGI-4 - 66,000 BTU Output Cast Iron Boiler, Spark Ignition - Series 4 (Natural Gas)

Weil-McLain CGI-4 Gas-Fired Water Boiler – Model 381359004

The Weil-McLain CGI-4 is a gas-fired, cast iron sectional boiler designed for closed-loop, hot water hydronic heating systems. Rated at 84% AFUE and equipped with intermittent electronic ignition, this unit delivers dependable performance and long service life for residential heating applications requiring up to 66,000 BTU/hr output. It supports natural gas operation and includes field conversion components for propane compatibility.

Design & Operating Characteristics

• Heat Exchanger: Cast iron, sectional construction with push-nipple design for watertight seal and efficient heat transfer
• Combustion System: Atmospheric draft burner with intermittent electronic ignition for energy-saving standby operation
• Venting: Natural draft via chimney; Category I venting with rear flue outlet standard
• Fuel: Natural Gas (LP conversion kit included)
• Ignition: Electronic, intermittent pilot with integrated flame sensor
• Safety Control: Factory-installed low water cutoff (probe-type)

Performance Specifications

• Model: CGI-4 (381359004)
• DOE Heating Capacity: 74,000 BTU/hr
• Net I=B=R Output: 66,000 BTU/hr
• AFUE: 84%
• Working Pressure: 50 PSI maximum (30 PSI ASME relief valve included)
• Flue Diameter: 4 inches (rear outlet)
• Supply/Return Connections: 1-1/4" NPT
• Electrical: 120V, 60Hz, single phase

Installation Notes

This unit is factory-assembled and pressure tested prior to shipment. The boiler must be installed on a non-combustible base and requires adequate clearance for service and combustion air. All gas piping, venting, and hydronic connections should follow Weil-McLain installation manuals and comply with applicable local and national codes.

Combustion air and venting must be configured for gravity venting into a lined masonry or B-vent chimney. The CGI-4 is not designed for sidewall or direct vent applications. A combustion analysis is required at startup to verify proper burner adjustment.

Control & Operation

• Aquastat: Combination high-limit and circulator control
• LWCO: Probe-type low water cutoff pre-installed
• Circulator: Not included (field-supplied)
• Service Access: Removable front panel for burner tray and ignition module access

Certifications & Standards

• CSA certified (ANSI Z21.13/CSA 4.9)
• ASME Section IV “H” stamp heat exchanger
• AHRI certified performance data
• Meets U.S. Department of Energy efficiency requirements for gas-fired hot water boilers

Summary

The Weil-McLain CGI-4 boiler offers reliable, mid-efficiency performance in a space-saving format, ideal for retrofit or new construction residential hot water heating systems. It features cast iron durability, built-in combustion safety, and a straightforward control platform—making it a practical solution for contractors requiring consistent performance and code-compliant safety features in an atmospheric gas boiler design.